Rising incidences of Systemic and Topical Mycosis caused by different genus of yeast fungi and dermatophytes in both immuno-deficient and immuno competent patients remain an important and inadequately addressed medical problem. Resulting mortality and alarming prolonged morbidity is of great concern. With all the drugs discovered thus far, there have been problems of limited spectrum, poor potency, limitations of suitable formulations, adverse drug reactions and life-threatening toxicities and quite often a combination of some or all of the above problems. Polyene aminoglycoside group of antibiotics appeared most promising broad-spectrum and potent. However, toxicities of most of these compounds prevented there inclusion as therapeutics.
Amphotericin B has been the only polyene Macrolide that stayed in wide clinical use despite the fact that various formulations such as sodium deoxycholate miceller suspension, liposomal, lipid complex and lipid colloidal dispersion, all contain life-threatening nephrotoxicity to varying extant.
The objectives in formulating Amphotericin B, are to remove nephrotoxicity, make stable preparation, ensure effectiveness at low doses and free of toxicity and adverse drug reactions even at high doses.
Large number of patents granted/filed and publications describing Amphotericin B formulations exist. Except for the below described four formulations no other formulations are operational as they have not been able to make such other formulations adequately nephro/safe.
In all the known Amphotericin B formulations, the constituents are selected from large list of options of phospholipids/lipids and stabilizers. No preparation is infused in saline as Amphotericin B is known to precipitate in saline.
1. Conventional Amphotericin B: Amphotericin B-Deoxycholate colloidal suspension in 5% Dextrose, Efficacy 33% Nephrotoxicity 67%
Amphotericin B is insoluble in aqueous medium. The problem was marginally overcome in late 1950s by dissolving Amphotericin B in deoxycholate and formulating as micellar suspension in 5% dextrose in water. Amphotericin B precipitates in NaCl and thus neither Amphotericin B in deoxycholate was prepared in NaCl nor diluted in saline. Furthermore, this suspension was lyophilized to render stability to the preparation.
2. Liposomal Amphotericin B diluted in 5% Dextrose Efficacy 77% Nephrotoxicity 20%
A Liposomal Amphotericin B made up of combination of soya phosphatidylcholine hydrogenated, distearoylphosphatidylglycerol, cholesterol and alpha tocopherol in 4.5% sucrose and disodium succinate hexahydrate as buffer was selected from amongst number of combinations of phospholipids, sterols, membrane stabilizing sugars and their varying ratios. Despite use of membrane stabilizing sucrose, this preparation was lyophilized to overcome instability. This preparation of Liposomal Amphotericin B is reported to precipitate in saline and thus dilution in/contact with saline is strongly forbidden.
U.S. Pat. No. 4,766,046 describes that:
Due to the size and, instability of Amphotericin B liposomes, it has not been possible to prepare and store small-diameter Amphotericin B liposomes without a significant (several fold) size increase over a several week storage period. As a result, due to different in vivo liposome uptake and drug release and toxicity properties which are related to liposome size, it has been difficult to control and evaluate the therapeutic index of stored Amphotericin B liposomes. The size instability problem is particularly serious where liposome sizes greater than 1-2 microns are attained, since cholesterol-containing Amphotericin B liposomes are substantially more toxic than smaller, original size liposomes. The size stability problem has been solved heretofore only by administering the sized liposomes shortly after preparation. This, of course, is an impractical approach to drug delivery in the usual clinical setting.
3. Amphotericin B Lipid Complex diluted in 5% Dextrose Efficacy 34% Nephrotoxicity 63%
This preparation is composed of Amphotericin B, synthetic phospholipids viz. Dimyristoylphosphatidylcholine and Dimyristoylphosphatidylgycerol. The aqueous suspension is diluted in 5% dextrose before administration. Neither the efficacy nor toxicity profile is improved over conventional Amphotericin B.
4. Amphotericin B Colloidal Dispersion diluted in 5% Dextrose Efficacy 46% Nephrotoxicity 40%
Amhotericin B and Sodium Cholesteryl Sulphate lyophilized with Tromethamine, Disodium edentate dehydrate and Lactose monohydrate HCl.
Glucose present in Amphotericin B Lipid formulations markedly reduces the beneficial effect of the topically applied formulation. The inhibitory mechanism of glucose is implied to be related to high viscosity introduced by glucose or to changes introduced by glucose on the lipid/water interface of colloidal particles (Crowe J H et. al. 1988 Biochim. Biophys Acta. 947:367-384). Even therapeutic success of Liposomal Amphotericin B at best is 77% which is sub par to present invention.
It was therefore, envisaged to replace dextrose with saline in this invention which has additional advantage of reducing Amphotericin B nephrotoxicity. In view of the well known and documented fact that Saline causes precipitation of Amphotericin B1-4, lipid composition and lipid to drug ratio were uniquely designed to ascertain that Amphotericin B in the nanosomes is immobilized to prevent precipitation of the nanosomal drug.